When sending a text message and the recipient of the message was not the intended recipient. Alternatively, when you try to reply to one person, and another message comes in just as you're about to reply, and you end up replying to the wrong person. This issue can have detrimental effects.

Girl to married guy: "Hey, what are you up to?"
(Guy is getting ready to reply, when he's distracted for two seconds, during which time, the following message hits his phone."
Wife to her husband: "I made it to Dallas."
(Now husband, thinking he's replying to his girlfriend says)
Husband to his wife (slip of the thumbs): "Nothing, my wife is out of town if you want to sleep over tonight."
Wife to husband: "WTF!?!?!"